The present invention relates generally to disk drive based data storage systems. More particularly, the present invention relates to modular disk drive expansion capabilities for computers.
Most computers employ Winchester (hard) type disk drives to store programs and data. The data capacity of the particular disk drive depends on the user""s anticipated storage requirements. It is often difficult to add data storage capability to a computer system once it has been configured. This difficulty is usually more dominant with personal computer type systems, but can present itself with work stations, as well as larger systems.
External disk drive storage systems, which were often referred to as xe2x80x9cBernouli Boxesxe2x80x9d, have provided the capability for adding an external disk drive to replace or augment the internal disk drive of a personal computer or work station. Several different data protocols have been adapted for use in conjunction with external data storage systems. These protocols are used in some systems to transfer data between internal components as well. The most popular of these protocols are the Small Computer Systems Interface (SCSI) and Enhanced Small Device Interface (ESDI). The SCSI and ESDI protocols and associated hardware allow data flow at rates of several megahertz, whereas Disk Operating System (DOS) data transfer rates have difficulty achieving these data transfer rates. Transfer rates of 5 megahertz or more are fairly common using the SCSI interface.
In most systems, a single power supply is coupled to a number of individual peripheral components including disk drives. The capacity of the system power supply is predetermined, and is based on the expected load that the system is anticipated to draw. Increasing the number of peripheral devices, or the capacity of peripheral devices such as disk drives results in a requirement for additional power which may have been unanticipated. As a result, it may be necessary to replace the power supply once it has been determined that it is necessary to expand the system capabilities.
When the power supply capabilities are expanded, an attempt is made to determine whether the new power supply will accommodate the future power supply requirements of the system. Future expansion beyond the anticipated load necessitates replacing the power supply again.
When hard disk drives were originally introduced, failure of the hard disk drive to maintain data, or to be able to recover the data was not uncommon. As a result, most users instituted rigid back-up programs using removable media such as floppy disk drive and tape back ups. As hard disk drives have become more reliable, many users have reduced their reliance on backing up the data stored within the system.
Hard disk drives have also increased in capacity from relatively modest levels of 10 megabytes to higher density, higher capacity levels approaching 2000 megabytes, and beyond. Backing up a hard disk which held 10 megabytes may have been reasonably time consuming, but backing up a hard disk which may have 100 or 200 times as much data becomes significantly more time consuming. As a result, users have become less diligent in their efforts to back up data from a hard disk drive.
This has resulted in an increased exposure to the user of a computer system should a single hard disk drive crash, or otherwise cease to function properly. The amount of data which may be irretrievably lost can be enormous. The consequences to the system user can be catastrophic. Data recovering centers exist, but may or may not be able to successfully recover the data from a particular hard disk drive, or may take several months to do so. Given the timelines of information in most applications, this becomes unacceptable.
It is therefore an object of the present invention to provide an easily expandable hard disk drive storage system which can be easily added to without requiring replacement of a power supply, or other integral components.
It is a further object of the present invention to provide a modular expansion system so that the entire system""s capability in the future is not restricted by choices made when the system is initially purchased.
It is a further object of the present invention to provide the capability for versatile selection of data transfer systems and organization.
It is a further object of the present invention to provide a high speed data transfer capability between the computer and external peripherals such as disk drives.
It is a further object of the present invention to provide a data storage system from which the data can be easily recovered, or reconstructed should a single hard disk drive fail.
It is a further object of the present invention to provide a versatile disk drive storage system which can be easily expanded after it is in use without sacrificing the data recovery capability of the system.
One feature of the present invention involves the use of a modular design in which peripheral devices such as hard disk drives are added in uniform stackable modules which include self contained power supplies. The individual modules interconnect mechanically to form a single structure which can be easily added to, or subtracted from.
Another feature of the invention involves the use of a number of individual, short interconnection cables to connect each of the modules together in order to route electrical power between the modules, as well as routing data transfer signals.
Another Embodiment of the present invention distributes data to be stored amongst three or more individual hard disk drives in order to allow data recovery from the remaining hard disk drives if a single hard disk drive ceases to function.